Laser safety standards Flashcards
What is the main set of UK Regulations for laser safety?
The Control of Artificial Optical Radiation at Work Regulations 2010 (AOR10).
What are some of the main requirements of AOR10?
Requires employers to:
- Assess risk of adverse health effects to eyes and skin.
- Eliminate or reduce risks below exposure limit values.
- Inform and train staff.
- Provide health surveillance and medical examinations where appropriate.
What are some other sets of legislation relevant to lasers?
- Health and Safety at Work act.
- Management of Health and Safety at Work Regulations.
- Personal Protective Equipment at Work Regulations.
- Reporting of Injuries, Diseases and Dangerous Occurrences Regulations.
- Control of Substances Hazardous to Health Regulations (due to plume).
What sort of things do the equipment classification laser safety standard cover?
- Safety measures.
- Warning devices.
- Instructions for use.
- Occupational safety.
- Light hazards.
- Wavelengths.
- Light emission.
- Markings.
- Symbols.
- Classification systems.
List some things that are covered in laser safety standards.
- Classification and requirements.
- Laser guards.
- Safe use.
- Eye protection.
- Drapes and patient protective covers.
- MPE/NOHD/eyewear calculations.
- Control measures.
- Hazards.
- Incidents.
What does laser classification relate to? When might a quoted class be invalid?
- Generally depend on the accessible emission limits (AELs).
- As the laser class is increased, the level of hazard and risk increases.
- Modifying a device can invalidate class.
What is the MPE? What does the MPE depend on?
- Maximum permissible exposure.
- Safe level of laser radiation that the eye or skin (different levels for eyes and skin) can be exposed to before adverse health effects.
- MPE depends on wavelength, exposure time and observation geometry.
What is AEL? How do they relate to laser classification?
- Accessible emission limit.
- AELs are derived from MPEs.
- Accessible emission of the laser (maximum level of laser radiation accessible) is compared against the AEL for classification.
What time basis is used for laser classification?
- 0.25 s blink response for 400 - 700 nm (visible).
- 100 s for aversion response for non-visible.
- 30 000 s where intentional long-term viewing is inherent in design.
What limiting aperture and measurement distances are used for laser classification for the naked eye in the retinal hazard region (400 - 1400 nm)? When would different values be required?
- 10 cm measurement distance with 7 mm aperture.
- 10 cm is the closest distance that still gives a sharp image on the retina.
- 7 mm is the size of the dilated human pupil.
- Different values would be required if viewing aids (e.g. telescopes, binoculars etc.) were used.
Describe a class 1 laser and provide examples.
- Typically safe under reasonably foreseeable conditions of use due to low laser emission or total enclosure.
- AEL class 1.
- Completely enclosed lasers.
Describe a class 1M laser.
- Safe due to geometrical spread unless magnifying aids used. M stands for magnifying optics.
- AEL class 1.
Describe a class 1C laser.
- No risk to eyes providing laser remains in contact with target tissue or material. C stands for contact.
- AEL class 1.
Describe a class 2 laser and provide examples.
- Visible radiation hazardous for eyes but protection afforded by aversion response.
- AEL class 2.
- Supermarket barcode scanner, some laser levelling devices.
Describe a class 2M laser and provide examples.
- Safe due to geometrical spread and aversion response unless magnifying aids used.
- AEL class 2.
- Laser for CT scan positioning.
Describe a class 3R laser and provide examples.
- Exceed Class 1 invisible and Class 2 visible limits but safety afforded by preventing direct exposure. R stands for relaxed.
- AEL class 3.
- Alignment lasers for building work.
Describe a class 3B laser and provide examples.
- Harmful to eyes (and skin at upper limits) but safety afforded by avoiding direct exposure to beam and specular reflections.
- AEL class 3.
- Physiotherapy and broadband sources.
Describe a class 4 laser and provide examples.
- Beam and diffuse reflections harmful to eyes and skin and can cause fire hazard and plume.
- AEL class 4.
- Surgical lasers.
What are the manufacturer’s requirements for class 3B/4 lasers?
- Remote interlock.
- Emission warning.
- Beam stop.
- Key-switch.
- Safety documentation.
- Labelled (true for all except class 1).
What additional UK requirements are there fore class 3B/4 lasers?
- Laser standby.
- Aiming beam.
- Audible/visible beam on indicator.
- Aperture label.
- NOHD.
- Beam divergence and anticipated change over time.
- Output power indication.
- Remote interlock connector.
- Specified calibration.
- Specified eye protection.
- Emergency stop.
- Shrouded footswitch.
What is the issue with only using optical density for eyewear specification?
It provides a protection level but not a damage threshold.
What do UK laser eyewear markings include?
- Wavelength range.
- Test condition (D = continuous wave, I = long pulsed, R = Q-switched, M = mode-locked).
- Protection factor.
- Approved inspection body test mark.
- Conformity test mark.
How long does laser protective eyewear protect from continuous wave and pulse laser radiation?
- CW: 5 s.
- Pulsed laser: 50 pulses.
